She shrugged. “If we sit here, it will be eighty-eight days till sunset. If we walk, it will be less.”

“Walk around half of Mercury?”

“Less than half, because we will be walking and the planet will be rolling. That’s the point. I mean, what else are we going to do? I’m not going to sit here for three months!” She was almost in tears, he saw.

“How far is it again?” he asked, thinking half of Titanas he said it. His stomach contracted within him.

“About two thousand kilometers. But if we walk east at, say, thirty kilometers a day, we shorten the wait time to something more like forty days. So we can cut it in half. That seems worth it to me. And it doesn’t have to be continuous walking. I mean, it’s not like the sunwalkers. We walk a day’s worth, eat, sleep a night, then walk again. Set a daily schedule. If we hiked for twelve hours out of every twenty-four, that would be a lot, but it would save even more days. What, Pauline?”

“Can you turn up Pauline’s voice again?” Wahram requested.

“I don’t want to now. She says twelve-hour days of walking would shorter our time down here by around forty-five days. That’s enough for me.”

“Well,” Wahram said. “That’s a lot of walking.”

“I know, but what are you going to do? Sit here for over twice as long?”

“No,” he said slowly. “I guess not.”

Although really it would not be so very long. A rereading of Proust and O’Brian, a few times through the Ring cycle; his little wristpad was very well stocked. But the way she stood there looking at him, these were not thoughts he felt comfortable expressing.

“I’ll turn up Pauline,” she said, as if giving him something in exchange for his agreement.

“ Solvitur ambulando,” Pauline said. “Latin for ‘It is solved by walking.’ Diogenes of Sinope.”

“Thus you prove motion is real,” Wahram supposed.

“Yes.”

Wahram sighed. “I was already convinced.”

Back at the first underground station they took stock. The three sunwalkers were perfectly happy to walk for six or seven weeks; it was very like their usual mode of existence. Their names were Tron, Tor, and Nar. They were gender nondescripts as far as Wahram was concerned, and seemed to him very young and simple. They lived only to hike around Mercury; they seemed to know nothing more than that, or perhaps they didn’t speak much to strangers. But what they did say seemed childlike to him, or provincial in the extreme. There were whole terraria filled with such folk, of course, but he had gotten used to thinking of the Mercurials as highly sophisticated, steeped in history and art and culture. Now he was learning that it was not universally true. He realized he had thought sun worshippers would be followers of the various early solar religions of ancient Egypt, Persia, the Inca—but no. They just liked the sun.

It looked like they were going to have to spend a couple of nights sleeping on the floor of the unimproved tunnel in between each way station. “Every third day,” Swan said, “we can resupply. It sets a good goal.”

“We might even be able to go farther,” Tron said shyly.

Tron was the one with the broken arm, so Wahram refrained from mentioning that for him personally, thirty-three kilometers a day might prove enough, or too much. That he might be the drag on this group was discouraging. In any case Swan was overseeing the filling of backpacks she had found in the emergency supply cabinets: their spacesuit helmets, some emergency air, water bottles, food, air mattresses, a little pot and stove. A roll of aerogel blankets, not very warm-looking, but the utilidor would stay at this temperature, Swan said; and it was pretty warm.

So: tunnel walk. Possibly similar to spelunking expeditions of long duration. Little headlamps were included in the packs too, although for now they were not necessary, as the ceiling held a warm square of yellow-white light every twenty meters or so, illuminating the rough rock of the utilidor very well. They were about fifteen meters underground, Swan said. The tunnel had been drilled through bedrock or regolith, with a heat finish that had imparted frequent swirls and dashes of mineral color, reminiscent of the cut surfaces of certain meteorites. In some stretches silver curves lay over pewter, then jet black. The floor had been chipped to a texture that made for a good grip underfoot. The tight curve of Mercury meant that the most distant overhead lights merged into a single bar of light. It was as if they could see the arc of the planet, which Wahram found vaguely encouraging. He was finding the idea of thirty-three kilometers a day, for more than forty days in a row, daunting. Must recall they were down around the forty-fifth latitude south here, so the distance was not as far as it would have been if they were on the equator. Sometimes Terminator’s tracks went even farther south, as he recalled. Things could be worse.

So. Walk for an hour, in a tunnel that changed very little, and only in iterative ways. Stop, sit on the ground, rest for a while; then walk an hour more. At the end of three hours, stop and eat. Already that interval felt very long, something like a week or more in ordinary human time, in the time of thinking. But they did that three times before stopping to eat a larger meal, then slept for eight or nine hours.

Hour, hour, hour; hour, hour, hour; hour, hour, hour.

The sensation of lengthening time grew very strong in Wahram. Why it should feel so long was hard to tell; the repetition of the elements of the day he would have thought might streamline and thus speed the hours; but no. Instead it was protraction, a very pronounced feeling of protraction. At the end of each day, as he settled down, footsore and exhausted, to sleep, he could stretch out on his air mattress and say, “One down, thirty-seven to go,” or even “thirty-three to go,” and feel a little stab of despair. Every hour felt like a week! Could they endure it?

The sunwalkers usually hiked a bit ahead, and by the time Wahram and Swan joined them at a stop, they were always prepping tea. Then, well before Wahram was ready to get up and go again, the young ferals were off, almost apologetically, with a nod and a wave. His days, therefore, were spent mostly with Swan.

She was clearly not happy at the prospect of this hike, even though it was her idea. She was doing it only because the alternative was worse, in her estimation. It was something to be endured, in misery mute or voluble. Some days she went ahead, some days fell behind. “I’m going to get sick at some point,” she said once. It became clear to Wahram that she liked the situation even less than he did—far less than he did, as she told him herself. She hated it, she said; suffered from claustrophobia; could not stand to be indoors; needed copious daily sunlight; needed lots of variety in her daily routines and in her sensory stimuli. These were necessities, she told Wahram, and in no uncertain terms. “This is so horrible,” she exclaimed often, making the word an emphatic three syllables with fore and aft stresses. “Horrible, horrible, horrible. I won’t be able to make it.”

“Let’s talk about something else,” Wahram would suggest.

“How can I? It’s horrrr-i-bull.”

Endless repetition of these points would still occupy only the first hour of their twelve-hour day of walking and rests. After such a first hour, Wahram would usually decide it was appropriate to point out that they would need to talk about something else if they were to avoid undue repetition stress on both their parts.

“Tired of me already?” Swan concluded from these observations.

“Not at all. Vastly entertained. Even interested. But this motif, of the unhappy voyage of necessity, it’s limited. It’s played out. I want a different story.”

“That’s lucky for you, because I was going to change the subject.”